Introduction. Sublingual immunotherapy is administered using allergens that contain varying amounts of antigen. Different manufacturers employ distinct application regimens. The study investigates the efficacy of “Antypollin”, a low-dose sublingual tablet containing birch allergen 0.1–1000 PNU combined with ascorbic acid.

   Materials and Methods. An open-label, comparative non-randomized trial was conducted involving 52 participants. We evaluated the effectiveness of sublingual tablets of birch pollen extract (1000 PNU) in relation to seasonal variations in pollen concentrations when used according to pre-seasonal–seasonal protocols for patients with seasonal allergic rhinitis. Additionally, the allergenic potency of these tablets was assessed by comparing them with solutions having known characteristics.

   Results. Allergenicity testing was performed on 40 subjects using prick tests with a solution of 1000 PNU/mL, resulting in an average papule diameter of 4 [IQR: 3–5] mm. This corresponded to approximately 50,000 EAA (Russian Unit of allergen activity). Total cumulative dose over the course amounted to 24,667 PNU, with half being administered prior to peak season onset. Specifically, within the first 42 days, 667 PNU were delivered, followed by two phases from day 43 to 66 and again from day 67 to 90, each providing 12,000 PNU. During the birch pollen period between April 28th and May 11th, 2025, annual mean pollen concentrations ranged from 1000 to 2500 grains per cubic meter. In the treatment group receiving Antypollin tablets, the Visual Analog Scale (VAS) score for rhinitis symptoms showed significantly lower values compared to controls (median VAS scores: 2 [IQR: 1–5] versus 7 [IQR: 4–8]; p < 0.001). Similarly, the total symptom-medication score (TCS) demonstrated significant improvement (p = 0.001), with median values of 12.7 [IQR: 8.3–18.1] versus 22.8 [IQR: 17.0–28.3]. At peak pollen period (April 21–27th, 2025), pollen levels reached up to 14,500 grains per cubic meter. During this phase, while VAS symptom scores remained statistically different (5 [IQR: 3–6.5] vs. 7 [IQR: 5–8]; p < 0.01), the TCS did not achieve statistical significance (88%; median difference: 22.3 [IQR: 11.6–22.8] vs. 23.0 [IQR: 17.0–28.4]; p = 0.12). In contrast, during alder flowering periods characterized by lower pollen concentrations, weekly averaged median TCS scores in the Antypollin group were significantly reduced compared to control groups (10.6 [IQR: 5.9–14.1] vs. 14.9 [IQR: 14.7–19.4]; p = 0.01). Nasal and conjunctival symptoms differed markedly (6 vs. 9; p < 0.05), although medication usage only trended toward differences (3.43 vs. 9.71; p = 0.07). Symptom severity, measured via VAS, was halved relative to controls. Nasal complaints exhibited a 30 % reduction in median values (3 vs. 6), whereas ocular symptoms decreased by 33 % (3.5 vs. 5), though these results did not reach statistical significance (p ranging from 0.06 to 0.12).

   Conclusion. The study demonstrated that birch pollen tablets combined with ascorbic acid exhibit sufficient allergenicity and serve as an effective therapeutic agent under conditions where pollen concentrations approximate annual average levels. Patient complaint rates and medication consumption should be adequate for analysis of efficacy. After completing the first course of therapy, it was observed that high pollen concentrations elicit similar clinical manifestations in both the treatment and control groups. This indicates insufficient therapeutic effect following a single course. It is likely that more prolonged courses of maintenance therapy will be required to achieve sustainable immunotherapeutic outcomes.